The invention relates to a constant velocity universal joint having a hollow outer part whose inner face comprises circumferentially distributed outer tracks, an inner part whose outer face comprises circumferentially distributed inner tracks and a spherical guiding face. Each outer track, together with the opposed inner track, receiving a ball for torque transmitting purposes, and having a cage which comprises a hollow spherical guiding face and an outer cage face. The cage is arranged between the inner face of the outer part and the outer face of the inner part and which guides the balls by means of windows. A first attaching part is connected to the outer part and close the joint towards one side. A second attaching part is provided in the form of a journal or shaft and which is connected to the inner part. A sealing boot is secured to the outer part on the one hand and to the second attaching part on the other hand and which closes the joint towards the other side, and enclosing a lubricant. The hollow cage, by means of its guiding face, is guided on the spherical guiding face of the inner part, with both of them, by means of their centers, being centered on the joint articulation center around which the outer part and the inner part carry out angular movements relative to one another.
Such constant velocity universal joints are typically covered by a sealing boot. The sealed joint is filled with lubricant which largely fills the free space between the joint components and between the sealing boot and the outer part and the second attaching element respectively.
As already described in DE-AS 22 05 798, boot failure results in a collapse of the lubrication system and thus, as a rule, in joint failure. With constant velocity universal joints which can only carry out angular movements, the boot has to bridge the entire space between the outer part and the second attaching element. During operation, there is a risk of the lubricant, in the course of time, largely collecting in the sealing boot. There is then no longer sufficient lubricant available at the parts which actually have to be lubricated and are in sliding contact with one another. Furthermore, the lubricant contained in the sealing boot constitutes a load on such parts because it rotates with them. This is the reason why it is proposed in DE-AS 22 05 798, additionally, to provide a further fixing point for the sealing boot at the cage. For this purpose, the cage is provided with a suitable projection. This measure reduces the mechanical load on the sealing boot, but does not solve the problem of providing sufficient lubricant in the regions actually to be lubricated.
It is therefore the object of the invention to provide a constant velocity universal joint wherein the parts which are in sliding contact with one another, especially the cage and inner part, are supplied with a sufficient amount of lubricant on their respective sliding faces.